Date: Fri, 12 Feb 2021 10:33:11 -0500 From: Fred Gleason <fredg@paravelsystems.com> Message-ID: <8782E03A-C352-44C0-8041-E6B16D28B869@paravelsystems.com> | If the first is true, then they should *never* change. Ever. For any | reason. I think, possibly aside from some very early changes (long long ago) that has always been true. Aside from any pedagogical reason, it is required to maintain backwards compatibility. | *Additional* ids can of course be introduced, That's all we ever do - both when a zone splits (what was one zone becomes two or more, because the rules which used to apply throughout the area covered by the zone will no longer be consistent), and second because for one reason or another there's to be a change of name. The "change" is always just the addition of a new ID, the old one remains. While we ignore the political nonsense most of the time, as the IDs are (kind of) arbitrary, they're also used to simplify maintenance. When someone tells us the the clocks in some part of the world are to alter on some specific (hopefully reasonably far future) date, it is much easier to be sure that the correct zone is being altered if it has a name that corresponds. If it weren't for that we might as well call the zones tzz1 tzz2 tzz3 ... kre